1. Field of the Invention
The present invention relates to a structure allowing for detection of a load applied to a vehicle seat. In particular, the invention is directed to such load detection structure for use in a vehicle seat slidable via a slide device.
2. Description of Prior Art
Recent years have witnessed a tendency for various automatically controlled functions and mechanisms to be increasingly incorporated in vehicle or automobiles, including safety devices such as air bags for protecting passengers against a great impact automatically in response to a collision, as well as various kinds of seat position adjustment devices for automatically adjusting the positions of seat sensitive to driver""s or passenger""s physiques and seating conditions. With such automated control innovations, there have been also found technical improvements to a passenger detection system for detecting the presence and absence of a passenger or driver in a seat of vehicle in advance before actuating or stopping the associated mechanical elements to automatically control various functions and mechanisms built in the seat.
Normally, the passenger detection system employs various sensors (e.g. a pressure sensitive element) which detect the weight of a passenger on a seat and emit a signal to electronic control systems for automatic control of various mechanical elements related to the seat. Most of the sensors are of a simple structure which can only sense the presence and absence of passenger on a seat, but the recent high-tech control technology inevitably requires that the sensors should further detect whether the passenger is an adult or a child as with air bag control system for instance.
To meet the demand, there have been proposed sensor systems for numerically detecting the weight of passenger or a corresponding load applied to the seat, determining whether the passenger is adult or child, according to a numerical data obtained, and then controlling and adjusting the associated mechanical elements to optimal conditions suited for the adult or child (e.g. controlling air bag), as disclosed from the Japanese Laid-Open Patent Publications Nos. 11-001153 and 11-304579. Namely, the Japanese Laid-Open Patent Publication No. 11-001153 shows a combination of an impact sensor and four load sensors, wherein each of the four load sensors is interposed between a slide rail device on which the seat is mounted and a support leg member fixed on the floor of vehicle. It also suggests an H-shaped base plate on which wiring of the load sensors is collectively arranged for electrical connection with another one cable. According thereto, the weight of an occupant on the seat is detected by the four load sensors in a collision case, and a signal emitted therefrom is determined by a control unit as to the numerical amount of the occupant""s weight, so that the air bag is adjusted in inflation according to the numerical data on the occupant""s weight, thereby realizing a proper inflation of air back to protect the occupant optimally according to his or her physique. On the other hand, the Japanese Laid-Open Patent Publication. No. 11-304579 discloses plural link mechanisms each having an arm pivoted therein, the link mechanisms being arranged between a slide rail fixed to a seat and a support base fixed on the floor of vehicle. In this prior art, a load sensor is provided at the free end portion of each arm of the link mechanism, such that a load applied vertically to the seat is imparted through the pivoted arm as an amplified or reduced vertical motion to the load sensor which then detects the amount of such vertical motion and determine a total weight of the seat and occupant on the seat. This reference states that a signal corresponding to the total weight may be emitted from the load sensors to a control unit associated with air bag and seat adjustment device, for instance.
However, the Japanese Laid-Open Patent Publication No. 11-001153 has no description on the mechanical structure of load sensor itself, and has no specific teaching on how the load sensor structurally supports the seat and how it actions to detect the seat occupant""s weight. This prior art is therefore neither realistic nor practical in assembling an optimal mechanical structure between the sensor and seat. The Japanese Laid-Open Patent Publication No. 11-304579 is found defective in that its link mechanism and pivoted arm are complicated in structure and further they occupy much of space heightwise between the seat and slide rail device, which results in the seat becoming large vertically in size and increasing its weight. Consequently, there remains a room of improvement in materializing a simplified and effective structure associated with this sort of load detection system.
In view of the above-stated drawbacks, it is therefore a primary purpose of the present invention to provide an improved load detection structure arranged at a slide rail device of a vehicle seat, which is greatly simplified in structure with reduced number of constituent element and effective in avoiding undesired increase in height of the seat.
In order to achieve such purpose, the load detection structure in accordance with the present invention includes a detection means for detecting a load applied from an occupant on vehicle seat, said detection means comprising:
a block member of a generally oblong shape extending its elongated body in the longitudinal direction thereof, the block member having a rigid yet elastically deformable property and including: an upper side; a lower side; a deflectable portion; and a base portion opposite to that deflectable portion; and
a strain gauge means fixedly attached on one of the upper and lower sides of block member;
wherein the block member is provided at a part of the movable rail element and extends therealong, such that the base portion of the block member is fixedly connected with such part of the movable rail element, whereas the deflectable portion thereof is operatively connected with the vehicle seat, whereby the load applied from the occupant on the vehicle seat is imparted to the block member, causing deflection of the deflectable portion of block member, and in response thereto, the strain gauge means detects an amount of such deflection and outputs a data which is a basis for determining a precise amount of the load corresponding to the amount of the deflection.
Accordingly, the load detection means is materialized simply by the block member and strain gauge means. Namely, it suffices only to fix one end portion of the block member to a slide rail device and movably connect another end portion of the same with the seat. Thus, the structure is quite much simplified, with a reduced number of required parts, thereby eliminating the assembling steps, making assembly of seat more rapid, and attaining reduction of whole costs involved. The block member may be of a generally oblong shape having a longitudinally elongated body, and therefore it can be attached on and along the foregoing part of movable rail element associated with the slide rail means, thereby avoiding the increase of whole height of the vehicle seat.
In the present invention, preferably, a link means may be provided between the vehicle seat and the slide rail means, extending along the foregoing part of movable rail element, so as to operatively connect the deflectable portion of block member with the vehicle seat and also securely connect the base portion of block member with the that part of movable rail element. More preferably, the link means may include a first connecting pin and a second connecting pin, and the said part of movable rail element may have a securing pin, with such an arrangement that the deflectable portion of block member is movably connected, via the first connecting pin, with one end part of the link means, while the block member base portion is not only fixedly connected with another end part of the link means via the second connecting pin, but also fixedly connected with the movable rail element via the securing pin.
Other various features and advantages of the invention will become apparent from reading of the descriptions hereinafter, with reference to the annexed drawings.